As you have probably noted, the Ukrainian situation is developing very fast.
The U.S. news reporting is totally biased. There is no real government at the national level in Kiev now, only a bunch of coup leaders. The Constitution is in abeyance since they overthrew the elected government by force.
The local areas are going their own way. Ukrainian troops seem to be going with the local people and governments.
The coup leaders are trying to whip up Western blood lust and war rage against Russia. If they are not insane, and they do not appear to be so, they know the whole Ukrainian military is not remotely able to stop Russia IF they really move in force against the coup leaders or local Ukrainian units in Eastern Ukraine.
Putin in fact is being very careful NOT to declare war or anything more than helping to save Russians from possible attacks. He is apparently quietly encouraging pro-Russian revolts against the anti-Russian revolts. IF this leads to open violence in predominantly Russian areas like Donetsk, I suspect Putin will send in low-key help as in the Crimea.
Putin is actually being very careful. The U.S. routinely sends in airborne Special Ops around the world to protect Americans in any such revolution, annihilates and invades whole nations like Afghanistan and Iraq on pretenses, etc.
I suspect Putin does not want to get involved in the Western Ukraine to avoid any serious guerrilla wars like they met in Afghanistan when they flew in unopposed on the invitation of the government but over the years got defeated by guerrillas.